Cockpit Deck Support Framing

jackryan · Post by **jackryan** » Jan 6th, '21, 21:41

I wanted to see if I can get some intel about the framing in the bilge that supports the cockpit deck. Does anyone know what kind of wood was originally used below the deck to hold the deck in position and give it support? Was this wood a good material to use below decks or was it a bad idea to have any wood supporting the deck? I am trying to decide if I should leave this wood in the boat if it's still in good shape, or remove it and replace with coosa or some other synthetic material. I'm sure I will have to remove some of this original wood, but it would simplify the project if I can leave the wood that's still in good shape.Thanks for any input and/or pic's of your below deck area before and after repairs.

Thanks!

JR

Tony Meola · Post by **Tony Meola** » Jan 6th, '21, 22:07

Jack

The supports are mahogany. When I redid my deck back in 96, we used mahogany again. Before installing we gave it a quick coat of glass to seal it. I had the deck out 2 years ago when I had the non skid redone. The wood was as good as the day we put it in.

Now if you want to make sure you do not have issues, and want to lighten up the stern a little, then I would order structural fiberglass from McMaster Carr and make the supports from that material.

I used the U Channel to build the rudder supports and the 90 degree angle material to redo the companion way supports.

I will tell you this the U Channel and the 90 Degree angle do not flex when you stand on them. We used the 3/8 material. If you want more support from those go to 1/2 inch.

https://www.mcmaster.com/fiberglass/str ... s-i-beams/

https://www.mcmaster.com/fiberglass/str ... -channels/

https://www.mcmaster.com/fiberglass/str ... nd-strips/

Carl · Post by **Carl** » Jan 7th, '21, 08:13

My uprights where Oak and the supports going along the top from stern to bulkhead were mahogany. I should add "I think". Unless the wood has a tag on it I really don't know one wood from another....a vague idea at best.

I had several uprights rotting as well as parts of the mahogany so I replaced everything as I was already tired of piece mealing repairs by then. All uprights I changed to fiberglass U-channel Tony linked you to, I think I used 3/16" X 1 x 3 and I had mahogany so just replaced. The uprights were 30 years old by that point...I guess I could have replaced with new Oak, but glassing made it a Do it once and never have to look at those upright again.

Of course the following year I realized the ethanol was eating my fiberglass tank and had to pull out the whole floor up including the uprights...but that is just the way things go for me at times.

Marshall Mahoney · Post by **Marshall Mahoney** » Jan 7th, '21, 11:19

I found that any wood near hatches that was routinely wet due to rain, washdown etc. was bad. I replaced a bunch of supports with kiln dried pressure treated wood. Held up good for 15 years but now getting a few soft spots. I will be going back with fiberglass. Treated wood supports that I replaced in the cabin are still pristine.

David Davidson · Post by **David Davidson** » Jan 10th, '21, 05:30

I used aluminium (English spelling!) box section throughout under my deck. No rot worries.

John F. · Post by **John F.** » Jan 10th, '21, 08:44

I used mahogany that's bigger dimensionally than what was in there, saturated with West and through bolted with stainless and nylon lock nuts. It looks like new after 7 years or so. There's a place about 20 minutes from where I live where I can get virtually any type of hardwood, and get it cut. Its bigger, stronger, and better done than what was in there, and that lasted 40 years and was still useable, so she's good

Carl · Post by **Carl** » Jan 10th, '21, 09:03

Aluminum as you said does not rot, but it does corrode.
Also if fastening with SS hardware...the two materials do not get along in a salt water environment...or maybe they do. In time they join to become one over time, unless isolated with something like Tuff-gel.
Done right, it can hold up well. I saw Aluminum as too much work over fiberglass structural which can be bolted or "glued" together with little to no prep and no maintenance.

Then again...I was in such a rush to get the wood out, so as never to have to deal with rotting wood again. What I forgot is that wood was in there 30+ years at the time with most of it still in great shape. The only parts that rotted where areas around the hatches that had issues and not properly addressed. I still have original wood under my deck on the outer stringers. I'm guessing 1x 6 that runs the full length that the deck sits on. It looked perfect 12 years ago when I did the deck...so I left it. It looked great when I put deck back in this year..so I added a shim over the top and continue to use.

saburke17 · Post by **saburke17** » Jan 10th, '21, 15:53

Tony Meola wrote: ↑Jan 6th, '21, 22:07 Jack

The supports are mahogany. When I redid my deck back in 96, we used mahogany again. Before installing we gave it a quick coat of glass to seal it. I had the deck out 2 years ago when I had the non skid redone. The wood was as good as the day we put it in.

Now if you want to make sure you do not have issues, and want to lighten up the stern a little, then I would order structural fiberglass from McMaster Carr and make the supports from that material.

I used the U Channel to build the rudder supports and the 90 degree angle material to redo the companion way supports.

I will tell you this the U Channel and the 90 Degree angle do not flex when you stand on them. We used the 3/8 material. If you want more support from those go to 1/2 inch.

https://www.mcmaster.com/fiberglass/str ... s-i-beams/

https://www.mcmaster.com/fiberglass/str ... -channels/

https://www.mcmaster.com/fiberglass/str ... nd-strips/

Tony do you happen to have any pics of your supports? maybe during construction. I have just removed my engines and my stringers that were replaced were done very poorly. They had a big dip in the middle and pitched 3 different ways

Tony Meola · Post by **Tony Meola** » Jan 10th, '21, 21:41

I believe I do have some. Let me take a look through my picture files. I know I lost some when my cell phone decided to take a swim through the washing machine.

Ironworker · Post by **Ironworker** » Jan 11th, '21, 13:34

Very timely topic. I have purchased a sheet of Coosa 3/4" Bluewater 26 to replace sections of my boat that was rotted. Most is in pretty good shape and eventually will all be replaced if I repower. Right now I'm just replacing the sections that need to go.

My concerns with various products other than wood is the ability for the screws to stay put.

saburke17 · Post by **saburke17** » Jan 11th, '21, 14:40

Thanks Tony, ill be starting a new thread on my winter project

mike ohlstein · Post by **mike ohlstein** » Jan 11th, '21, 15:38

I used 5/4" Mahogany about 15 years ago. Still looks great. Untreated......

Carl · Post by **Carl** » Jan 11th, '21, 20:15

mike ohlstein wrote: ↑Jan 11th, '21, 15:38 I used 5/4" Mahogany

Between wood, lumber and plumbers pipe sizes...it's enough to drive a person off the edge.

5/4". What nobody took math Reduce Reduce.

A 2x4 ain't 2x4 and 1" pipe ain't 1" on the outside like 1" tube nor is it1" on the inside. K I n d a c l o s e though...

A life rant over. . . For now

pschauss · Post by **pschauss** » Jan 12th, '21, 09:45

And then there's the Whitworth system.

Carl · Post by **Carl** » Jan 12th, '21, 13:25

The Whitworth threads are not so bad, its just a different thread form. Luckily, I rarely do much repair work anymore so I don't get to see them as its an old antiquated system, same with British Pipe Threads.

mike ohlstein · Post by **mike ohlstein** » Jan 12th, '21, 15:12

Nobody knows what five quarter is?

A 2x4 may be a 1.5x3.5, but 5/4 lumber is 1.25"

Carl · Post by **Carl** » Jan 13th, '21, 18:33

Yes I know what 5/4 is...just saying it's a stupid name. As is 2x4...really who cares what it was.

I will say at least 5/4 is what it says it is.

Tony Meola · Post by **Tony Meola** » Jan 13th, '21, 21:48

Carl

Notice you no longer walk into Home Depot and by 1/2 plywood. The Home Depot by me now shows its actual dimension. I heard someone took them to court for trying to scam them.

You can not make this stuff up.

jackryan · Post by **jackryan** » Jan 14th, '21, 10:45

Awesome posts guys. I'm heading over to the boat to take a look this morning. I'm interested to see whats below deck, as the decks have not been off since 1978 (when the boat was built).

JR

Ironworker · Post by **Ironworker** » Jan 14th, '21, 11:05

jackryan wrote: ↑Jan 14th, '21, 10:45 Awesome posts guys. I'm heading over to the boat to take a look this morning. I'm interested to see whats below deck, as the decks have not been off since 1978 (when the boat was built).

JR

This might be the scariest post I've ever read on the INET!

pschauss · Post by **pschauss** » Jan 14th, '21, 13:43

Carl wrote: ↑Jan 12th, '21, 13:25 The Whitworth threads are not so bad, its just a different thread form. Luckily, I rarely do much repair work anymore so I don't get to see them as its an old antiquated system, same with British Pipe Threads.

Actually, I was referring to the wrench sizes. A 3/8" Whitworth wrench has a span of 0.701". The 3/8" marking indicates the diameter of the bolt you are tightening or loosening.

Carl · Post by **Carl** » Jan 14th, '21, 20:36

pschauss wrote: ↑Jan 14th, '21, 13:43 Actually, I was referring to the wrench sizes. A 3/8" Whitworth wrench has a span of 0.701". The 3/8" marking indicates the diameter of the bolt you are tightening or loosening.

Oh shoot me now, that's just downright stupid. Hell I think I just insulted stupid people. Maybe myself included. So your saying they have wrenches for common size hardware based on the hardware size.

So I come up to a bolt head I need to remove..it looks to be 1/2"...now I have to guess the size of the bolt under the head I'm not 100 % sure is... Dumb and dumber.

Sounds like the crap people who think they are smart think of, to make life easier for the dumb people smarter then they are.

jackryan · Post by **jackryan** » Jan 15th, '21, 00:12

I made it out to the boat this afternoon to check out the situation below the deck. A lot of the deck support stringers were were in bad shape, especially at the ends of the boards. I’ll try to post a few pictures. These first two pics are the backside of the deck and hatches with Coosa that has been covered with fiberglass on both sides. My fiberglass guy is planning on using resin and micro spheres on the back side of the deck panels to fill the gaps between the Coosa and edge of the deck panels. These seem very solid.

https://i.imgur.com/jxaUdWk.jpg

https://i.imgur.com/k0wq7QN.jpg

This next pic is an overview of the below deck area:

https://i.imgur.com/yBXuxTu.jpg

As you can see the deck
Stringers are in rough shape and will need to be replaced. I need an opinion from the experts here. I was wanting to go back with a similar deck stringer set up to what’s currently in the boat, just replace the wood with Coosa encapsulated with glass. My fiberglass guy wants to go a completely different direction. Instead of going back with a stringer system that the deck sits on, he wants to use Coosa and fiberglass to fabricate stringers that are integral to the bottom of the deck panels and connect those to the hull stringers with 1/4” aluminum pieces that are the same dimension as the wooden supports that currently connect my old deck stringers to the hull stringers. Here are two pics of the wooden supports that I’m referring to that connect the deck support stringers to the hull stringers:

https://i.imgur.com/FAfmePw.jpg

https://i.imgur.com/TT3SO50.jpg

As I said, he wants to eliminate the stringers that the deck sits on, fabricate new stringers to the back side of the newly reinforced deck panels and then connect those to the hull stringers with 1/4”aluminum plates, in the place of the current wooden supports. The idea is intriguing, but I am skeptical that this will be able to create a stable deck long term. He plans to eliminate the outermost stringers and glass L bracket supports directly to the hull along the port and starboard sides for the deck panels to sit on. I’m not sure I am explaining this in an understandable way, but hopefully you guys get the idea. This guy is gifted with fiberglass and has built boats and replaced many decks before, so he does have some experience doing this sort of thing. Hopefully you guys are able to view the pics-I’ve never tried Imgur before.

Fire away with questions if you don’t understand my description

JR

pschauss · Post by **pschauss** » Jan 15th, '21, 12:50

Carl wrote: ↑Jan 14th, '21, 20:36 Oh shoot me now, that's just downright stupid. Hell I think I just insulted stupid people. Maybe myself included. So your saying they have wrenches for common size hardware based on the hardware size.

So I come up to a bolt head I need to remove..it looks to be 1/2"...now I have to guess the size of the bolt under the head I'm not 100 % sure is... Dumb and dumber.

Sounds like the crap people who think they are smart think of, to make life easier for the dumb people smarter then they are.

Exactly what I thought fifty years ago when I was trying to fix the transmission on my '59 Norton. I was going crazy trying to find socket wrenches to fit the nuts and bolts until one of my friends told me about the Whitworth system.

John F. · Post by **John F.** » Jan 15th, '21, 13:52

Just an idea:

http://bertram31.com/newbb/viewtopic.ph ... ck#p100169

Tony Meola · Post by **Tony Meola** » Jan 15th, '21, 21:34

Jack

Tell him keep it simple. You want to make sure that you can easily remove the deck should you ever need too.

Snipe · Post by **Snipe** » Jan 18th, '21, 13:00

Jack this is what I did don’t know if it will help. I have a three piece glasstec deck. The belly band all the way around the cockpit and stringers as well as bulkeds are all coosa and 1708 all work was done with west system. https://imgur.com/gallery/5oh8D7H

Ironworker · Post by **Ironworker** » Jan 18th, '21, 16:58

Snipe wrote: ↑Jan 18th, '21, 13:00 Jack this is what I did don’t know if it will help. I have a three piece glasstec deck. The belly band all the way around the cockpit and stringers as well as bulkeds are all coosa and 1708 all work was done with west system. https://imgur.com/gallery/5oh8D7H

Snipe,

I will be forever grateful to you for posting these photos. Many thanks!

saburke17 · Post by **saburke17** » Jan 19th, '21, 19:35

Very nice work Snipe, on a side note. Are the decks meant to be perfectly flat?

Snipe · Post by **Snipe** » Jan 20th, '21, 09:09

The deck pitches aft. The level in the picture was used a straight edge. I followed the height of the original deck at the engine bulked to the bottom of the scuppers. As far as port to starboard it is flat.

jackryan · Post by **jackryan** » Jan 28th, '21, 00:24

I decided to keep it simple and go with the original stringer layout. I am going to go back with mahogany stringers coated with two coats of gray Interlux 2000 barrier coat. The original stringers lasted 43 years and had no coating at all on them.

I am wondering if most 31 Bertram's originally came with the same deck stringer layout that my boat did. I have 6 wooden stringers---to identify them, I will call the outer most stringer on the port side #1 and count across to the starboard side, so that the outer stringer on the starboard side is #6.

The two outer stringers (stringer #1 and stringer #6) were plywood stringers that were tabbed weakly to the hull with fiberglass. The mahogany stringers that I am replacing these with should be a substantially stronger and longer lasting material.

Working toward the middle of the boat, the next two stringers (call them stringer 2 and 5) were attached to the hull with wooden uprights (you can see these uprights clearly in picture #4 and #5 if you go back and look at my post on Jan. 15th) We are a little puzzled by these two stringers because they sit several inches lower than the two inner stringers (stringer #3 and #4) and several inches lower than the outer stringers (#1 and #6) To us its not adding up why stringers #2 and #5 sit lower, unless at that point, the deck does not sit directly on the stringer, but instead the lip of the hatch opening sit on the stringer. The lip of the hatch openings hang a couple of inches below the deck.

Do you guys know if stringers #2 and #5 sit lower because the lip of the hatch openings sit on these stringers?? You would think I would have clearly known this after owning the boat for 14 years, but I never studied the underside of my deck. My brother and I unsuccessfully searched old pictures to see if we could find one with the hatches open to see if stringers 2 and 5 were visible when the hatches were open.

I was not there when my fiberglass guy removed the decks, and sadly he didn't take a pic of the underside of the deck after he removed them. We are thinking that the lip of the hatch openings must sit directly on stringer #2 and #5--is that why those two stringers sit lower? We will dry fit the 3 deck sections once we have the new mahogany stringers installed, but it would be nice to know in advance why stringer 2 and 5 are lower than the other stringers.

As always, Many Thanks for the great insight I get from the faithful!!

JR

P.S.--Snipe, thanks for posting the pics of your under deck area. Simply beautiful!

Ironworker · Post by **Ironworker** » Jan 28th, '21, 10:01

Jack,

If it will help, I can send you photos of my deck supports? You are using the term stringer but I suspect you're talking about the deck supports.

jackryan · Post by **jackryan** » Jan 28th, '21, 10:59

Ironworker-

Sure, that would be great, thanks. You got me thinking about the term "stringer." These are, as you say, definitely "deck supports." Several others referred to them as stringers, and my brother is a mechanical engineer and he has been calling them stringers as well. Here is the definition of a stringer I found on line:

A stringer is a longitudinal structural piece in a framework, especially that of a ship or aircraft.

I guess these could be considered stringers, as they are longitudinal structural pieces in the framework that supports the deck.

Anyway, thanks for the offer and I look forward to the a picture of your deck supports.

JR

Carl · Post by **Carl** » Jan 28th, '21, 12:35

When I think boat Stringer I think of the big fiberglass "beams" integral with the hull running stern to bow. The stringers straddle the fuel tank, its what the engine beds are mounted to.

The part your talking about I guess is a stringer too...

Ugh...

hmmm maybe "hull stringer" and deck support stringer

jackryan · Post by **jackryan** » Jan 28th, '21, 12:38

I agree, when I think stringer, its the structural beams on the hull. I think using "deck support" will eliminate confusion.

JR

Yannis · Post by **Yannis** » Jan 28th, '21, 14:14

Jack,

Aren't there obvious marks of the 2 and 5 supports on the under side of the deck pieces?
If not, then I would assume that they were not meant to support the deck!

jackryan · Post by **jackryan** » Jan 29th, '21, 10:07

Hi Yannis,

Sadly, I wasn't there when the decks came off and my guy didn't take a picture of the bottom side of the decks when he removed them. He removed the balsa core on the back side of the deck and replaced it with coosa covered with fiberglass, so now theres no way to tell what was on the back side of the deck. You can see pictures of the back side of my partially finished decks on my Jan 14th post.

We are working on the deck supports today and tomorrow. I hope to have them in the boat this weekend. Once the new deck supports are in, we will be able to dry fit the 3 deck pieces and see where they fall in relation to supports 2 and 5. I'll let you know how it works out.

JR

Tony Meola · Post by **Tony Meola** » Jan 29th, '21, 22:30

Jack

When ran strings across the deck to make sure when we set them in place they were level with each other. Tap finishing nails into the outboard stringer on each side directly across from each other. Then when you set the beam in place make sure it just kiss's the string. That will help you make sure you are level.

jackryan · Post by **jackryan** » Feb 7th, '21, 00:40

Tony,

What a great idea! It will be another week or two before we fasten the decks in, but we will def. employ your leveling technique. As of this morning, we have the decks back in temporarily. I made the hour run back to the south shore today. We still have some below deck work to do, but I am extremely impressed with the results of the new decks and deck supports. They are extremely stable and have a nice solid feel to them. The stringers are painted with gray Interlux 2000 and are looking great--the old deck supports made it nearly 50 years with nothing on them. With the Interlux 2000 and a cockpit cover, these should make it another 100 years

I'm off to India via New York tomorrow. Hopefully it doesn't snow two feet like it did when I was up there last week. I'll get some pics of the new stringers posted here when I get back from my trip.

JR

Tony Meola · Post by **Tony Meola** » Feb 7th, '21, 21:40

Jack

We had 7 inches today. Not the 20 some odd inches of last week. More snow being called for mid week. Going to get bitter cold.